1. Field of the Invention
The present invention relates to a magnetic tape cassette for a cleaning tape cassette usable for video and audio appliances. More particularly, the present invention relates to the construction of half casings for the casing of a magnetic tape cassette or a cleaning tape cassette.
2. Discussion of Background
A conventional magnetic tape cassette usable for, for instance, video appliances comprises a casing formed of a pair of upper and lower half casings and reel hubs rotatably supported in the casing to wind and rewind a magnetic tape, the reel hubs being received in the casing. In order to receive the reel hubs rotatably in the casing, relatively large reel areas are formed at the central portion of the inner surface of the base plate of each of the half casings so that the reel hubs on which the magnetic tape is wound are positioned there. However, when the reel area portions which occupy the major portion of the base plate are formed to have a large wall thickness, a relatively large amount of resin is required, whereby the weight of thus produced casing increases. Further, resin powder is apt to produce due to the mutual friction between the casing and the reel hubs because the reel areas contact with the reel hubs in a surface contact relation.
The inventors of this application have proposed in Japanese Utility Model Application No. 155636/1988 an invention wherein a number of ribs are formed in the reel areas in the inner surface of base plate of the half casings so as to form recesses which reduce substantially the wall thickness of the half casings.
In the half casings having a number of ribs formed in the reel areas of the half casings, however, there was a problem in the outer appearance of the product thus formed, such that there easily caused irregularity in glossiness on the outer surface of the base plates at position corresponding to the ribs formed in the inner surface of the base plates. The above-mentioned problem of the irregularity in glossiness can be more or less improved by forming a coarse surface on the outer surface of the base plates. However, there is a restriction in designing the half casings, and there is also a limitation in determining the roughness of the outer surface of the half casings. Further, in a case that the depth of the recesses formed by forming the ribs is small, an amount of resin used for injection molding the half casing can not be greately reduced and it is not effective to reduce the weight of the casing.